High speed drum printer with stepping motor to advance drum and paper

ABSTRACT

SIGNALS, A COUNTING DEVICE FOR APPLYING DRUM POSITION INDICATING SIGNALS TO EACH OF SAID COMPARING DEVICES, MEANS FOR APPLYING DATA SIGNALS TO EACH OF SAID COMPARING DEVICES, PULSING MEANS FOR CONCURRENTLY CAUSING STEPPING OF SAID COUNTING DEVICE AND SAID COUNTER, MEANS OPERABLE BY SAID STEPPER MOTOR DURING MOVEMENT OF A SECOND PART OF SAID PERIPHERY OF SAID DRUM PAST SAID PRINTING DEVICES FOR ADVANCING SAID RECORD MEDIUM FROM ONE LINE PRINTING POSITION TO A NEXT, MEANS CONTROLLED BY SAID DRUM AFTER SAID ADVANCEMENT OF SAID RECORD MEDIUM FOR PROVIDING AN INDEX SIGNAL, AND MEANS RESPONSIVE TO SAID INDEX SIGNAL FOR RENDERING SAID PULSING MEANS INEFFECTIVE.   1. A DATA PRINTER COMPRISING A ROTATABLE TYPE DRUM HAVING A PLURALITY OF COLUMNS OF TYPE CHARACTERS THEREON, SAID TYPE CHARACTERS EXTENDING ABOUT A FIRST PART ONLY OF THE PERIPHERY OF SAID DRUM, PRINTING DEVICE ASSOCIATED WITH RESPECTIVE ONES OF SAID COLUMNS FOR TRANSFERRING AN IMPRINT OF ANY OF SAID TYPE CHARACTERS IN RESPECTIVE ONES OF SAID ROWS ONTO A RECORD MEDIUM, A STEPPER MOTOR FOR INCREMENTALLY ROTATING SAID TYPE DRUM TO SUCCESSIVELY POSITION DIFFERENT ONES OF SAID TYPE CHARACTERS IN PRINTING RELATION TO SAID PRINTING DEVICES. COMPARING DEVICES FOR COMPARING DRUM POSITION INDICATING SIGNALS AND DATA SIGNALS AND FOR CAUSING OPERATION OF RESPECTIVE ONES OF SAID PRINTING DEVICES WHEN SAID DRUM POSITION INDICATING SIGNALS CORRESPOND TO SAID DATA

i United States Patent [1 1 [111 3,838,638 Clary 1 091-1919 1 HIGH SPEED DRUM PRINTER WITH STEPPING MOTOR TO ADVANCE DRUM Elaminerwilliflm Penn AND PAPER Assistant Examiner-E. M. Coven [75] Inventor: John G. Clary, Pasadena. Calif.

[73] Assignee: Addmaster Corporation, San

Gabriel. Calif. [57] ABSTRACT A parallel data printer including a type drum having [22] Flled: 1972 columns of type characters thereon. The drum is in- [21] Appl. 223 475 crementally driven by a stepper motor under control of a pulsing device. Such pulsing device also advances a counter which emits drum position indicating sig- [52] U.S. Cl. 101/93 nals' Denominationany arranged comparator Circuits [51] lift. Cl 99 J93 C cause actuation of respective print hammers when Fleld of Search 10 161 matches occur between different data signals and the drum position indicating signals. A portion of the type drum is left blank to permit advancement of the paper References cued by the stepper motor after printing has occurred. A UNITED ST T S PATENTS signal under control of the drum causes resetting of 3,331,316 7/1967 Bretti 101/93 C the counter and stopping of the motor upon comple- 3,420,166 1/1969 Ellis et al. 101/93 C tion of a revolution of the drum, preparatory to print- 3,415,184 l2/l968 Perucca 101/93 C i h next li f type 3,505,950 4/1970 Harper 101/93 C 3,654,859 4/1972 Touchman 101/93 C 6 Claims, 4 Drawing Figures 3,656,427 4/1972 Foley 101/93 C 3,673,955 7/1972 Curtiss et a1. lOl/93 C HIGH SPEED DRUM PRINTER WITH STEPPING MOTOR TO ADVANCE DRUM AND PAPER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to high speed parallel data printers, such as are used in connection with data processing equipment, and has particular reference to a data printer embodying a rotatable print drum including a plurality of denominationally arranged columns of type characters extending around the periphery thereof. As selected type characters in different denominational columns pass a printing line, imprints from such type characters are transferred to a paper strip.

2. Description of the Prior Art Heretofore, high speed parallel data printers have generally been of the print-on-the-fly type wherein a printing drum having a columns of type characters thereon is rotated at a constant speed and as selected type characters pass the printing line, type hammers are actuated to imprint the paper against such type characters.

Since the type drum is moving at a constant speed, extremely accurate timing must be effected in actuating the hammers to produce an acceptable line of print. Both mechanical and electrical devices have been employed herefore to actuate the print hammers. Mechanical hammer actuating devices are generally complicated and expensive while electrical hammer actuating devices are subject to different adverse operating conditions which could effect the timing, such as variations in temperature, vibration, deterioration of electrical components, etc.

Also, such timing is difficult to maintain over exi tended periods of time, thus requiring at least occasional adjustments.

Also, print-on-the-fly printers tend to smudge the imprint of the type characters since the hammers maintain the paper in contact with the type characters for a finite period of time while such underlying type characters are in movement.

Further, prior art parallel printers generally require clocking or timing circuits controlled by the drum to indicate the instant drum position at all times.

SUMMARY OF THE INVENTION type drum is rotated one complete revolution during I the printing of each line of print but the type characters extend only partly around the periphery of the drum, the remaining portion being left blank to allow for advancement of the paper.

A further feature of the invention is the absence of a clocking or timing circuit under control of the drum to indicate the position thereof as each row of type characters approaches the printing line.

Accordingly, a principle object of the invention is to provide a simple and relatively inexpensive, high speed, parallel data printer.

Another object is to eliminate the need for precise timing of actuation of type hammers, such as is required in printers having a constantly rotating type drum.

Another object is to provide a parallel data printer of the above type having a single stepper motor for both rotating the type drum and for advancing the paper relative to a printing line.

A still further object is to eliminate the need for a clocking or timing device controlled by the type drum for controlling the actuation of the type hammers.

BRIEF DESCRIPTION OF THE DRAWINGS The manner in which the above and other objects of the invention are accomplished will be readily understood in reference to the following specification when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a transverse sectional view through a parallel data printer embodying one form of the present invention.

FIG. 2 is a schematic view of the printer and controls therefore.

FIG. 3 is a transverse sectional view showing the hammer retracting bail and drive cam therefore.

FIG. 4 is a view similar to FIG. I. but with parts omitted and illustrating a modified form of the invention.

DESCRIPTION OF THE EMBODIMENT SHOWN IN FIGS. 1 TO 3 Referring particularly to FIGS. 1 and 2, the printer shown therein comprises a type drum 11 having a plurality of columns of raised type characters 12 extending around a portion of the periphery thereof, each column containing a complete numerical font of type characters ranging in value from 1 to 9 and 0. Similar characters in the different columns are also arranged in rows extending along the length of the drum, i.e., all are located in one row, all are located in a next adjacent row, etc.

The type drum 11 is incrementally rotated by a stepper motor 13 in the direction of arrow a. The motor 11 may be of conventional construction and is suitably controlled by a controller switch unit 14 also of conventional construction. Pulses applied to an input line 15 are distributed by the switch unit 14 to incrementally advance the motor 11.

In the embodiment shown in FIGS. 1 to 3, the motor 13 advances the type drum 24 steps per revolution, i.e., 15 per step. Such motor and control switch unit 14 may be obtained commercially, for example, from the Superior Electric Co. of Bristol, Connecticut.

A plurality of denominationally arranged printing hammers 16 are aligned with respective ones of the columns of type characters 12. Such hammers are independently pivoted on a common stationary shaft 17 and have aligned imprinting heads 18 located in front of a printing ribbon 20 which extends along the length of the drum 11. A paper strip 21, forming a record medium, is fed from a suitable supply roll (not shown) and is guided by a guide chute 22, between a feed roll 23 of elastomeric material or the like and a pressure roll 24, the latter being effective to maintain the paper 21 t frictional engagement with the roll 23. The paper strip is further guided by a second chute 25, between the ribbon and the periphery of the type drum 11.

The printing hammers 16 are independently urged clockwise by tensioned springs 26 but are normally held in their illustrated cocked positioned by latches 27 forming the armatures of electromagnets 28, 29, etc. Each of the latches 27 is pivotally supported at 30 on a magnet frame 31 forming part of the associated electromagnet and is urged clockwise by a tensioned spring 32 into engagement with a latching shoulder 33 formed on the respective print hammer. Adjacent hammers are differently shaped and the respective electromagnets are staggered about the shaft 17 to permit closer lateral spacing of the hammers 16 than would otherwise be possible. The various magnets 28, 29, etc., are supported by cross braces 131 forming part of the printer framework.

Upon energizing an electromagnet, i.e., 28, its latch 27 will release the respective print hammer 16 to the action of its spring 26, causing the print head 18 to impact the adjacent portions of the ribbon 20 and paper 21 against an underlying type character 12 so as to imprint such character on the paper. During the latter part of this impacting movement, the lower end of the hammer 16 strikes a relatively stiff leaf spring 34 supported by the adjacent brace 13]. The spring 34 then yields to permit printing impact but then immediately returns the hammer slightly in a counterclockwise direction to eliminate smudging or phantom printing.

Means are provided to recock the hammers 16 during the latter part of a revolution of the drum 11, and after the various type characters have passed the printing line. For this purpose, a recocking bail 36 (see also FIG. 3) is provided which extends along the length of the type drum 11 and has downwardly extending arms 37 pivotally supported on the shaft 17. Rollers, one of which is shown at 40, on the bail arms 37 engage cams 41 mounted on shaft 140 which also carries the feed roll 23. A mutilated gear 42 on the stepper motor shaft 19 is arranged to mesh with a full gear 43 mounted on the shaft 40.

Shortly after passage of the last row of type characters 12 past the printing line, located behind the ribbon 20, the multilated gear 42 engages and drives the gear 43 to rotate the feed roll 23, and cams 41 one quarter revolution in a clockwise direction and thus cause one of four equi-spaced lobes 39 on each of the cams 41 to rock the bail 36 and thereby rock print hammers counterclockwise until the latter are recocked by the latches 27. During such recocking movement, the feed roll 23 advances the paper strip 21 to a new print line position. Suitable detent means (not shown) is provided to locate the feed roll 23 and earns 41 in one of their four angular positions, as shown in FIG. 3, after advancement of the gear 43 by the mutilated gear 42.

Although the control circuitry for the printer is shown' for illustration purposes as being operable according to the binary coded decimal system, it will be apparent to those skilled in the art that with obvious modifications other types of coded circuits could be used, such as decimal coded input circuitry.

As shown in FIG. 2, denominationally arranged groups 240 of four binary weighted lines each are connected to respective comparator circuits 241 of conventional construction. Comparator circuits 241 are also connected in parallel to a group 49 of four binary weighted lines which are connected to the outputs of successive stages of a four-state binary counter 143. The latter counter is stepped by a pulse generator 44 through an And gate 45 which is under control of a flipflop 46. Pulses applied to the counter 143 are also applied over line 15 to step the motor 13 concurrently with the stepping of the counter.

Indexing means is provided to initially establish isochronism between the type drum 11 and the counter 143 and to stop the drum and reset the counter at the end of a complete revolution of the latter as it reaches its initial position shown in FIG. 1. For this purpose, a magnetic mark 47, which may also take the form of a permanent magnet slug, is formed on the type drum l1 and is adapted to generate an indexing pulse in a magnetic sensor or pick-up head diagramatically indicated at 48 during a step of the motor 13 just prior of movement of the type drum 11 into its initial position. Sensor 48 transfers such indexing pulse over a line 50 to reset the counter 143 and to reset the flip-flop 46 so as to close And gate 45.

It will be noted that in the initial position of the type drum 1]. the leading row of type characters is located one step removed from the printing line.

When the printer is initially placed into operation, a false print command pulse is applied over a line 51 to set the flip-flop 46 to open gate 45, causing the pulse generator 44 to pulse the stepper motor 13 and counter until the type drum 11 moves into its position shown in FIG. 1 at which time an index pulse generated in sensor 48 is applied over line 50 to reset the counter 143 and flip-flop 46 to arrest the motor. Thereafter, binary coded decimal signals, representing a number to be printed, are applied in parallel over the various groups of data lines 240 and a true print command pulse is applied over line 51 to set the flip-flop 46 to concurrently step the motor 13 and counter 143. When a match occurs between data signals applied over one or more of the groups of data lines 240 and drum position indicating signals applied over the group of lines 49, representing the selected type character or characters arriving at the printing line, an output signal is applied over a line 52 from the appropriate comparator unit or units 241 to the respective electromagnet or electromagnets i.e., 28, 29, etc., to fire the respective hammer or hammers 16 and thus cause an imprint.

A suitable delay circuit 53 may be placed in series in circuit with the line 50 to insure that the hammers 16 are fired only when the type drum 11 is at rest.

After all of the type characters 12 have passed the printing line, the pulse generator 44 will continue to step both the motor 13 and the counter 143, causing gear 42 to drive shaft to recock the hammers 16 and advance the paper as noted herebefore. Although the counter 143 will be further stepped during the continued advance of the motor to its initial position, no further printing can occur even though data signals may continue to be applied to the data input lines 240 since the print hammers will be in the process of being moved to recocked positions by the time the counter 143 has recycled.

Just prior to the end of a complete revolution of the type drum 11, the index mark 47 will generate an indexing pulse to reset the counter 143 and flip-flop 46, thus arresting the motor in its initial illustrated position.

FIG. 4 illustrates a modified form of the printer in which elements similar to those shown in FIGS.1 to 3 we identified by similar reference numbers. In this case, a full gear 54 is substituted for the multilated gear 42 of FIG. 1. Gear 54 is in continual mesh with a gear 55 attached to the paper feed shaft 140 so as to rotate the shaft 140 one complete revolution during each revolution of the type drum. A partial paper feed roll 56 is located so that during the first part of a revolution of the type drum 11 and while printing is occurring, the feed roll will be ineffective to advance the paper 21, while during the latter part of the revolution of the type drum and after printing has been completed, the raised portion of the feed roll will advance the paper to the next print line. Also, the hammer recocking cams are modified as shown at 58 to rock the recocking bail 36 at the start of the second half revolution of the shaft 40, after the printing operation.

Although the printer is disclosed as having a numerical printing font only, it will be apparent that the printer could be readily modified to incorporate an alpha-numerical or other printing font as well.

I claim:

1. A data printer comprising a rotatable type drum having a plurality of columns of type characters thereon,

said type characters extending about a first part only of the periphery of said drum,

printing devices associated with respective ones of said columns for transferring an imprint of any of said type characters in respective ones of said rows onto a record medium,

a stepper motor for incrementally rotating said type drum to successively position different ones of said type characters in printing relation to said printing devices,

comparing devices for comparing drum position indicating signals and data signals and for causing oper ation of respective ones of said printing devices when said drum position indicating signals correspond to said data signals,

a counting device for applying drum position indicating signals to each of said comparing devices, means for applying data signals to each of said comparing devices,

pulsing means for concurrently causing stepping of said counting device and said counter, means operable by said stepper motor during move ment of a second part of said periphery of said drum past said printing devices for advancing said record medium from one line printing position to a next,

means controlled by said drum after said advancement of said record medium for providing an index signal, and

means responsive to said index signal for rendering said pulsing means ineffective.

2. A data printer according to claim 1 comprising means responsive to said index signal for resetting said counter to an initial counting position.

3. A data printer according to claim 2 wherein said index signal providing means provides said index signal when the first of said type characters in said rows are located one step removed from said printing devices.

4. A data printer comprising a rotatable type drum having a plurality of columns of type characters thereon,

said type characters extending about a first part only of the periphery of said drum,

printing devices associated with respective ones of said columns for transferring an imprint of any of said type characters in respective ones of said rows onto a record medium,

a stepper motor for incrementally rotating said type drum to successively position different ones of said type characters in printing relation to said printing devices,

comparing devices for comparing drum position indicating signals and data signals and for causing operation of respective ones of said printing devices when said drum position indicating signals correspond to said data signals,

a counting device for applying drum position indicating signals to each of said comparing devices,

means for applying data signals to each of said comparing devices,

pulsing means for concurrently causing stepping of said counting device and said motor,

means operable by said stepping motor during movement of the remaining part of saidperiphery of said drum past said printing devices for advancing said record medium from one line printing position to a next,

means operable after said advancement of said record medium and prior to movement of a first of said type characters in cooperative relation with a respective one of said printing devices for providing an index signal,

means responsive to said index signal for rendering said pulsing means ineffective, and

means for selectively rendering said pulsing means effective.

5. A data printer according to claim 4 wherein said record medium advancing means comprises a record medium drive roller,

a (first) driven gear operatively connected to said roller, and

a drive gear for driving said driven gear,

said drive gear having gear teeth about a portion only of the periphery thereof,

said drive gear being operable to drive said driven gear only after passage of all the said type characters past said printing devices.

6. A data printer according to claim 4 wherein said record medium advancing means comprises a drive roller engagable with said record medium for advancing said record medium, and

means operable by said motor for rotating said roller,

said roller having a record medium engaging surface over a portion only of the periphery thereof,

said surface being arranged to advance said record medium only after passage of all the said type characters past said printing devices. 

